1. Field of the Invention
The present invention relates to a recording element unit, an ink jet recording element unit, an ink jet cartridge and an ink jet recording apparatus for driving the heat generating resistance member by using an individual electrode and a common electrode.
2. Related Background Art
As the recording element unit for use in an ink jet recording apparatus, there is already known a configuration shown in FIGS. 10A to 10C, which are respectively a plan view of the recording element unit; a cross-sectional view along a line 10B--10B in FIG. 10A; and a partial magnified view of a portion 10C in FIG. 10A.
The recording element unit 30 is provided with a substrate 20, a heat generating resistance layer 1, individual electrodes (wirings) 2, an insulation layer 3, a protective layer 4, a common electrode (wiring) 5, electrothermal converting members (heat generating resistance members) 6, external connection electrodes 7, a return electrode (wiring) 8, and an external connection electrode 9. In general, the wirings are formed with a large width in order to reduce the wiring resistance, while the heat generating resistance members are formed with a narrow width in consideration of the resistance, the heat generating area, etc. As shown in FIG. 10C, the heat generating resistance member 6 is formed by providing the heat generating resistance layer 1 with notches 11, 12 in a substantially symmetrical manner, so that the center 15 of the individual electrode 2 substantially coincides with the center 16 of the electrothermal converting member 6.
The above-mentioned recording element unit 30 is normally provided with a plurality of the heat generating resistance members 6, the common electrodes 5, the individual electrodes 2, and the external connection electrodes 7, 9.
In the recording element unit 30, an electric current is supplied to the heat generating resistance member 6 formed in the heat generating resistance layer 1 to generate thermal energy in the heat generating resistance member 6.
More specifically, the thermal energy can be generated in the electrothermal converting member 6 by sequentially supplying the driving current through the external connection electrode 7, the individual electrode 2, the electrothermal conversion member 6, the common electrode 5, the return electrode 8 and the external connection electrode 9. The ink jet recording element unit is to execute recording, utilizing such thermal energy for ink discharging. The ink jet recording element unit having plural electrothermal converting members can be employed for realizing an ink jet recording apparatus capable of recording plural dots at the same time, thereby achieving high-speed recording.
Because of the recent demand for the recording of high density and high speed, it is already common to execute the recording of the main scanning line simultaneously. Also because of the increasing demand for recording image data in addition to the character data and recording in color, there is already proposed a recording element unit having a high density array of a multitude of electrothermal converting members.
However, in the manufacture of the recording element unit having a high-density array of the electrothermal converting members, such electrothermal converting members have to be arranged with a constant pitch. Also, the high-density arrangement of the electrothermal converting members leads to a high-density arrangement of the individual electrodes, so that there will be left no room for the return electrode between the individual electrodes. Stated differently, the formation of the wiring for the return electrode becomes extremely difficult.